show the search term in the search box on a results page

Author: tomjn

sidebar.php

@@ -1,7 +1,7 @@
 <div class="book-summary">
 	<div id="book-search-input" role="search">
 		<form method="get" action="<?php echo esc_url( home_url() ); ?>">
-			<input type="text" name="s" placeholder="Type to search">
+			<input type="text" name="s" value="<?php echo esc_attr( get_search_query() ); ?>" placeholder="Type and press enter to search">
 		</form>
 	</div>
 	<nav role="navigation">